Signalling arrangement for telephone equipment

Abstract

Each of a number of remote subscriber telephones is connected through its own pair of lines, including ground lines, to a central office in the usual way. Each of many or all of the subscriber telephones has near it a special subscriber end equipment for doing a local job and connected across the related subscriber telephone. In the central office where the ground lines merge into a ground line going to one side of the standard direct current battery, supplying the remote subscriber telephones, there is a modulator in series in the ground line and effective to vary the voltage across the regular line pairs at a frequency or frequencies other than the voice frequency range but effective to actuate all of the special subscriber end equipments.

I claim: 
     
       1. A signalling arrangement for use with a telephone system having a plurality of subscriber telephones individually connected by voice frequency lines to a central office exchange and connected by battery lines at the central office exchange to a common electrical battery, comprising: a plurality of individual response devices each located adjacent a related one of said subscriber telephones, means for connecting each of said responsive devices in circuit with the respective one of said related subscriber telephones, means for amplitude modulating said battery lines at a non audible frequency recognizable by said responsive devices, and means for connecting said modulating device through said battery lines at the central office exchange to said voice frequency lines for recognition by said responsive devices.   
     
     
       2. a signalling arrangement as in claim 1 in which said modulating device is in series between said battery and said telephones. 
     
     
       3. A signalling arrangement as in claim 1 in which each of said responsive devices is in parallel with the related one of said subscriber telephones. 
     
     
       4. A signalling arrangement as in claim 1 in which said signal is substantially distinguished from the normal voltage of said battery and from battery voltage changes at said voice frequency. 
     
     
       5. A signalling arrangement as in claim 1 in which each subscriber telephone and the related one of said responsive devices is at the subscriber's premises and remote from said central office at which said modulator is located. 
     
     
       6. A signalling arrangement as in claim 1 in which said modulating device changes the voltage of said battery only in an amount permitting substantially normal operation of said subscriber telephones. 
     
     
       7. A signalling arrangement as in claim 1 in which said signal recognized by one of said responsive devices is at one chosen frequency other than voice frequency, said signal recognized by another of said responsive devices is at another chosen frequency other than said voice frequency, and said modulating device is effective to supply signals at said chosen frequencies. 
     
     
       8. A signalling arrangement as in claim 7 in which said modulating device is effective to supply signals at either of said chosen frequencies. 
     
     
       9. A signalling arrangement for use with a telephone system having a plurality of subscriber telephones individually connected by voice frequency lines to a central office exchange and connected by battery lines at the central office exchange to a common electrical battery, comprising: a plurality of individual responsive devices each located adjacent a related one of said subscriber telephones, means for connecting each of said responsive devices in circuit with the respective one of said related subscriber telephones, means for amplitude modulating said battery lines at a non audible frequency to provide different coded patterns to respective groups of correspondingly coded responsive devices associated with said telephones, and means for connecting said modulating device through said battery lines at the central office exchange to said voice frequency lines for recognition by said responsive devices.   
     
     
       10. A signalling arrangement as in claim 9 in which said modulating device is in series between said battery and said telephones. 
     
     
       11. A signalling arrangement as in claim 9 in which each of said responsive devices is in parallel with the related one of said subscriber telephones. 
     
     
       12. A signalling arrangement as in claim 9 in which said signal is substantially distinguished from the normal voltage of said battery and from battery voltage changes at said voice frequency. 
     
     
       13. A signalling arrangement as in claim 9 in which each subscriber telephone and the related one of said responsive devices is at the subscriber's premises and remote from said central office at which said modulator is located. 
     
     
       14. A signalling arrangement as in claim 9 in which said modulating device changes the voltage of said battery only in an amount permitting substantially normal operation of said subscriber telephones. 
     
     
       15. A signalling arrangement as in claim 9 in which said signal recognized by one of said responsive devices is at one chosen frequency other than voice frequency, said signal recognized by another of said responsive devices is at another chosen frequency other than said voice frequency, and said modulating device is effective to supply signals at said chosen frequencies. 
     
     
       16. A signalling arrangement as in claim 15 in which said modulating device is effective to supply signals at either of said chosen frequencies.